[PATCH 3/5] mm: Convert wp_page_copy() to use folios

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

Use new_folio instead of new_page throughout, because we allocated it
and know it's an order-0 folio.  Most old_page uses become old_folio,
but use vmf->page where we need the precise page.
---
 mm/memory.c | 65 ++++++++++++++++++++++++++---------------------------
 1 file changed, 32 insertions(+), 33 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 6099c786b5f9..dc8a6fd45958 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3043,8 +3043,8 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
 	const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;
 	struct vm_area_struct *vma = vmf->vma;
 	struct mm_struct *mm = vma->vm_mm;
-	struct page *old_page = vmf->page;
-	struct page *new_page = NULL;
+	struct folio *old_folio = NULL;
+	struct folio *new_folio = NULL;
 	pte_t entry;
 	int page_copied = 0;
 	struct mmu_notifier_range range;
@@ -3052,23 +3052,22 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
 
 	delayacct_wpcopy_start();
 
+	if (vmf->page)
+		old_folio = page_folio(vmf->page);
 	if (unlikely(anon_vma_prepare(vma)))
 		goto oom;
 
 	if (is_zero_pfn(pte_pfn(vmf->orig_pte))) {
-		struct folio *new_folio;
-
 		new_folio = vma_alloc_zeroed_movable_folio(vma, vmf->address);
 		if (!new_folio)
 			goto oom;
-		new_page = &new_folio->page;
 	} else {
-		new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma,
-				vmf->address);
-		if (!new_page)
+		new_folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma,
+				vmf->address, false);
+		if (!new_folio)
 			goto oom;
 
-		ret = __wp_page_copy_user(new_page, old_page, vmf);
+		ret = __wp_page_copy_user(&new_folio->page, vmf->page, vmf);
 		if (ret) {
 			/*
 			 * COW failed, if the fault was solved by other,
@@ -3077,21 +3076,21 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
 			 * from the second attempt.
 			 * The -EHWPOISON case will not be retried.
 			 */
-			put_page(new_page);
-			if (old_page)
-				put_page(old_page);
+			folio_put(new_folio);
+			if (old_folio)
+				folio_put(old_folio);
 
 			delayacct_wpcopy_end();
 			return ret == -EHWPOISON ? VM_FAULT_HWPOISON : 0;
 		}
-		kmsan_copy_page_meta(new_page, old_page);
+		kmsan_copy_page_meta(&new_folio->page, vmf->page);
 	}
 
-	if (mem_cgroup_charge(page_folio(new_page), mm, GFP_KERNEL))
+	if (mem_cgroup_charge(new_folio, mm, GFP_KERNEL))
 		goto oom_free_new;
-	cgroup_throttle_swaprate(new_page, GFP_KERNEL);
+	cgroup_throttle_swaprate(&new_folio->page, GFP_KERNEL);
 
-	__SetPageUptodate(new_page);
+	__folio_mark_uptodate(new_folio);
 
 	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm,
 				vmf->address & PAGE_MASK,
@@ -3103,16 +3102,16 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
 	 */
 	vmf->pte = pte_offset_map_lock(mm, vmf->pmd, vmf->address, &vmf->ptl);
 	if (likely(pte_same(*vmf->pte, vmf->orig_pte))) {
-		if (old_page) {
-			if (!PageAnon(old_page)) {
-				dec_mm_counter(mm, mm_counter_file(old_page));
+		if (old_folio) {
+			if (!folio_test_anon(old_folio)) {
+				dec_mm_counter(mm, mm_counter_file(&old_folio->page));
 				inc_mm_counter(mm, MM_ANONPAGES);
 			}
 		} else {
 			inc_mm_counter(mm, MM_ANONPAGES);
 		}
 		flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
-		entry = mk_pte(new_page, vma->vm_page_prot);
+		entry = mk_pte(&new_folio->page, vma->vm_page_prot);
 		entry = pte_sw_mkyoung(entry);
 		if (unlikely(unshare)) {
 			if (pte_soft_dirty(vmf->orig_pte))
@@ -3131,8 +3130,8 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
 		 * some TLBs while the old PTE remains in others.
 		 */
 		ptep_clear_flush_notify(vma, vmf->address, vmf->pte);
-		page_add_new_anon_rmap(new_page, vma, vmf->address);
-		lru_cache_add_inactive_or_unevictable(new_page, vma);
+		folio_add_new_anon_rmap(new_folio, vma, vmf->address);
+		folio_add_lru_vma(new_folio, vma);
 		/*
 		 * We call the notify macro here because, when using secondary
 		 * mmu page tables (such as kvm shadow page tables), we want the
@@ -3141,7 +3140,7 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
 		BUG_ON(unshare && pte_write(entry));
 		set_pte_at_notify(mm, vmf->address, vmf->pte, entry);
 		update_mmu_cache(vma, vmf->address, vmf->pte);
-		if (old_page) {
+		if (old_folio) {
 			/*
 			 * Only after switching the pte to the new page may
 			 * we remove the mapcount here. Otherwise another
@@ -3164,18 +3163,18 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
 			 * mapcount is visible. So transitively, TLBs to
 			 * old page will be flushed before it can be reused.
 			 */
-			page_remove_rmap(old_page, vma, false);
+			page_remove_rmap(vmf->page, vma, false);
 		}
 
 		/* Free the old page.. */
-		new_page = old_page;
+		new_folio = old_folio;
 		page_copied = 1;
 	} else {
 		update_mmu_tlb(vma, vmf->address, vmf->pte);
 	}
 
-	if (new_page)
-		put_page(new_page);
+	if (new_folio)
+		folio_put(new_folio);
 
 	pte_unmap_unlock(vmf->pte, vmf->ptl);
 	/*
@@ -3183,19 +3182,19 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
 	 * the above ptep_clear_flush_notify() did already call it.
 	 */
 	mmu_notifier_invalidate_range_only_end(&range);
-	if (old_page) {
+	if (old_folio) {
 		if (page_copied)
-			free_swap_cache(old_page);
-		put_page(old_page);
+			free_swap_cache(&old_folio->page);
+		folio_put(old_folio);
 	}
 
 	delayacct_wpcopy_end();
 	return 0;
 oom_free_new:
-	put_page(new_page);
+	folio_put(new_folio);
 oom:
-	if (old_page)
-		put_page(old_page);
+	if (old_folio)
+		folio_put(old_folio);
 
 	delayacct_wpcopy_end();
 	return VM_FAULT_OOM;
-- 
2.35.1